Impact of variations in solar activity on hydrological decadal patterns in northern Italy

Abstract

[1] Using spectral and statistical analyses of discharges and basin average precipitation rates acquired over the Po River since the early 1800s, we investigate the impact of variations in solar activity on hydrological decadal patterns over northern Italy. Wet and dry periods appear to alternate in accordance with polarized sunspot cycles. Intriguingly, a solar signature on Po River discharges is detected to be highly significant since the late 1800s, before the onset of sunspots hyperactivity established by the middle 1900s. In particular, observed hydrological patterns over northern Italy are significantly correlated, under periods of quiet sunspot activity, with parameters characterizing the Sun's orbital motion, specifically with the time derivative of the solar angular momentum (t) which is thought to modulate the strength of the solar wind and sunspot dynamics under weak sunspot activity. The North Atlantic Oscillation (NAO) is detected as potential link between the Sun and Po River discharges, since it is significantly correlated with both solar activity and the decadal variability in the north Italian climate. In particular, positive (negative) NAO anomalies, which are associated with comparatively lower (higher) Po River discharges, are assessed to alternatively correlate at decadal timescales either with t or with the Earth's geomagnetic activity (GA), which closely follows sunspot activity. This changing correlation seems to be regulated by the strength of sunspot activity: under periods of quiet sunspot activity, a weakening of the GA-NAO connection and a reinforcement of the t-NAO connection is observed. In this sense, the strength of solar activity apparently modulates the connection between the NAO and Po River discharges.

Holocene climate aridification trend and human impact interrupted by millennial- and centennial-scale climate fluctuations from a new sedimentary record from Padul (Sierra Nevada, southern Iberian Peninsula)

“…Sonett and Suess (1984) described a significant cycle in solar activity around ∼ 208 years (Suess solar cycle), which could have triggered our ∼ 200-year cyclicity. The observed ∼ 240-year periodicity in the Padul-15-05 record could be either related to variations in solar activity or due to the mixed effect of the solar cycle together with the ∼ 300-year NAO-interpreted cycle and could point to a solar origin of the centennialscale NAO variations as suggested by previously published research (Lukianova and Alekseev, 2004;Zanchettin et al, 2008). Finally, a significant ∼ 170-year cycle has been observed in both the Mediterranean forest taxa and Botryococcus times series from the Padul-15-05 record.…”

Long-term solar activity influences on South American rivers

“…Signals of solar activity have recently been found with spectral analysis techniques in the river Nile by Ruzmaikin et al (2006), who found a low-frequency 88-year variation present in solar variability and in the Nile records. Similarly, Zanchettin et al (2008) found that the discharge of the Po river appear to be correlated with variations in solar activity, on decadal time scales.…”

Multifractal Detrended Cross-Correlation Analysis of sunspot numbers and river flow fluctuations

“…Log-log plot of F (s) versus s for original streamflow and sunspot data sets by using DFA method (Figure ( [15,81]. Moreover, cycle of solar activity represented by sunspot is one of most robust effect which affects on streamflow fluctuations.…”